On the interplay between rotation, deformation and pairing

The influence of angular momentum on the extension of deformed regions is studied. Techniques based on the similarity between pairing rotational bands and ordinary rotational bands are used. Indications for an increase of deformation with increasing spin is obtained for rare-earth nuclei with neutron numbers N=88-90. The yrast states of odd and even nuclei and of positive and negative parity are compared on an absolute scale. It is found that, in the rare-earth region, the odd-even energy difference has almost disappeared for I>or=14. However, by considering both positive- and negative-parity yrast states, it is concluded that a substantial pairing gap exists also at higher spins. (23 refs).